In materials science, it is known that heat treatments can be used to alter the physical and/or chemical properties of a material. Heat-treatment techniques generally include annealing, case hardening, precipitation strengthening, tempering, and quenching. Annealing causes changes in material properties by heating and maintaining a suitable temperature Annealing can occur by the diffusion of atoms within a solid material Annealing can be used to induce ductility, relieve internal stresses, refine structure, and improve cold working properties.
It is recognized in some materials-science arts that annealing can be performed with inert gases. For example, U.S. Pat. No. 6,322,849, to Joshi et al., describes an inert-gas anneal to restore desired electronic and ferroelectric properties of a ferroelectric element. The inert-gas anneal is preferably performed after hydrogen-plasma processes, forming-gas anneal steps, and other high-energy steps of integrated circuit formation.
Synthesis gas (hereinafter referred to as syngas) is a mixture of hydrogen (H2) and carbon monoxide (CO). Syngas can be produced, in principle, from virtually any material containing carbon. Carbonaceous materials commonly include fossil resources such as natural gas, petroleum, coal, and lignite; and renewable resources such as lignocellulosic biomass and various carbon-rich waste materials. It is preferable to utilize a renewable resource to produce syngas because of the rising economic, environmental, and social costs associated with fossil resources.
There exist a variety of conversion technologies to turn these feedstocks into syngas. Conversion approaches can utilize a combination of one or more steps comprising gasification, pyrolysis, steam reforming, and/or partial oxidation of a carbon-containing feedstock.
Syngas is a platform intermediate in the chemical and biorefining industries and has a vast number of uses. Syngas can be directly combusted to produce heat and power. Syngas can also be converted into alkanes, olefins, oxygenates, and alcohols such as methanol, ethanol, and higher alcohols. These chemicals can be blended into, or used directly as, diesel fuel, gasoline, and other liquid fuels.
Since the 1920s it has been known that mixtures of methanol, ethanol, and other linear alcohols can be obtained by reacting syngas over certain catalysts (Fischer and Tropsch, Brennst.-Chem. 7:97, 1926). Later, Dow Chemical and Union Carbide jointly developed a sulfided mixed-alcohol catalyst based on MoS2 (Phillips et al., National Renewable Energy Laboratory TP-510-41168, April 2007). U.S. Pat. No. 4,752,623 (Stevens and Conway), originally assigned to Dow Chemical, discloses a cobalt-molybdenum-sulfide catalyst for producing mixed alcohols from syngas. However, known catalysts used for the conversion of syngas to alcohols can have limited yields and selectivities to particular alcohols (such as ethanol).
What are therefore needed are methods to increase yields and selectivities to particular alcohols, especially C1-C4 alcohols. It would be particularly beneficial for such methods to be capable of treating catalyst compositions in a practical manner, such as inside a reactor.